Innovation in domestic wastewater treatment by integrating 3D printed biocarriers into artificial wetlands

Poor domestic wastewater treatment in rural areas puts aquatic life and human health at risk due to microbiological contamination, accumulation of nutrients such as nitrogen and phosphorus, and the spread of waterborne diseases. Given this problem, various investigations have been carried out on wastewater treatment in these areas. Constructed wetlands have proven to be effective in wastewater treatment and offer ecological benefits, although they require regular maintenance, especially of gravel, which becomes clogged over time by organic matter and suspended particles. This obstruction reduces the efficiency of the wetland and requires cleaning or replacement of the gravel to restore its function. A promising alternative is the fabrication of 3D biocarriers, which could replace the gravel and mitigate these limitations. 3D printing has opened up new possibilities, allowing the creation of customized shapes and structures that optimize the performance of artificial wetlands. This study seeks to fabricate 3D printed biocarriers with a high surface area to volume ratio and a density higher than that of water. Horizontal flow subsurface constructed wetlands will be implemented for wastewater treatment in a pilot scale system. In this system, gravel will be used as a support medium in one wetland, while in two others, type I and type II biocarriers constructed with polymers (polypropylene and virgin and recycled polyethylene terephthalate) will be used. The porous geometry for 3D printing of the biocarriers will be based on triply periodic minimum surfaces (TPMS) that maximize the surface area while maintaining a high structural density and favoring the adhesion and growth of biomass. Subsequently, the effectiveness of the 3D printed biocarriers for the removal of contaminants will be evaluated, comparing the quality of the treated water in wetlands that use biocarriers with those that use gravel. To evaluate the impact of the biocarriers, biweekly measurements of water quality will be carried out, measuring physicochemical parameters such as pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids, turbidity, nitrogen and phosphorus. Microbiological analyzes will also be performed, with emphasis on fecal coliforms, before and after treatment. Monitoring will be carried out for six months, guaranteeing the representativeness of the data in both types of wetlands. Likewise, the hydraulic conditions of the wetland that incorporates the 3D printed biocarriers will be analyzed, evaluating factors such as surface load, hydraulic retention time and flow regime. These aspects are key to understanding performance in terms of treatment efficiency and long-term operational stability. For statistical analysis of the data, hypothesis tests, such as analysis of variance (ANOVA), will be used to compare the differences in contaminant removal between the two treatment groups. Regression tests will also be used to model the relationship between hydraulic variables and treatment efficiency. This study can contribute to the achievement of Sustainable Development Goal (SDG) 6, which seeks to ensure the availability and sustainable management of water and sanitation for all. In addition, it could serve as a basis for developing more economical and sustainable solutions for wastewater treatment in rural areas, improving water quality and reducing public health risks.

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